Carrier member for step selectors in tap changers

ABSTRACT

A TAP CHANGER FOR TRANSFORMERS HAS STEP SELECTORS AND LOAD CONNECTORS. THE STEP SELECTOR HAS A CENTER PART PROVIDED WITH CARRIER MEMBERS FOR MOVABLE CONNECTION CONTACTS AND SLIP RINGS FOR BRUSHES. THE CARRIER MEMBERS ARE FORMED OF TWO PARALLEL RODS OF INSULATING MATERIAL, BOTH MOUNTED TO TURN AROUND THE AXIS OF THE CENTER MEMBERS ARE ROD CARRIERS A NUMBER OF MOVABLE CONNECTING CONTACTS AND A CORRESPONDING NUMBER OF SLIP RINGS. THE TWO RODS ARE POSITIONED INSIDE THE SLIP RINGS SO THAT THEY CAN BE PIVOTED STEPWISE IN RELATION TO EACH OTHER THROUGH SUBSTANTIAL ANGLES.   D R A W I N G

March 20, 1973 s. NORMAN ET AL CARRIER MEMBER FOR STEP SELECTORS IN TAP CHANGERS 2 Shoats-Shaet 1 Filed June 9, 1972 March 20, 1973 s, NQRMAN ET AL. 3,721,895

CARRIER MEMBER FOR STEP SELEC'IORS TN TAP CHANGERS 2 Sheets-Sheet 2 F19 Filed June 9, 1972 32 l/ f 2 2/ 35 c2 5& I j 55} United States Patent 3,721,895 CARRIER MEMBER FOR STEP SELECTORS IN TAP CHANGERS Sivert Norman and Erik Hammar, Ludvika, Sweden, as-

signors to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden Filed June 9, 1972, Ser. No. 261,239

Claims priority, application Sweden, June 21, 1971,

8,013/71 Int. Cl. H02p 13/06; H01h 19/58 US. Cl. 323-435 R 2 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION (1) Field of the invention The invention relates to a carrier member for step selectors for tap changers.

(2) The prior art In such tap changers, during a switching operation the three mechanically connected contacts must be able to move independently of the other three contacts at least one step in each direction. Previously therefore the movable contacts have been placed on two concentric carrier members, at least the outer one comprising a tube. So that the contacts attached to the inner carrier member can move when the outer tube with its contacts is stationary, a number of sectors corresponding to the number of contacts on the inner carrier member must be cut out of the inner carrier member. Furthermore, it is extremely difiicult to assemble the contacts on the inner carrier, since this must be done after the inner carrier member has been fitted inside the outer one.

SUMMARY OF THE INVENTION The present invention relates to an arrangement for those tap changers for transformers which comprise step selectors and load connectors where the step selector comprises a centre part with carrier members for movable connection contacts and slip rings for brushes which are connected to the load connector. The carrier member consists of two parallel rods of insulating material, each of which is pivotable around the centre part and carries a number of movable connection contacts and a corresponding number of slip rings. The invention is characterised in that the two rods are placed inside the slip rings where they are stepwise pivotable in relation to each other.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the accompanying drawings in which FIG. 1 shows a side view of a central part for a three phase step selector and FIG. 2 shows an end view of the step selector with connections to a phase winding of the transformer and to the load connector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows that the centre part comprises two rods 1 and 2 of insulating material. The rod 1 is connected at its lower end to a bearing pin 3- journalled in a bearing, not shown. The rod 2 is journalled at its lower end on an upwardly directed part of the bearing pin 3 by means of a sleeve 4. Both rods are therefore pivotable around the axis of the centre part. At the upper part of the centre part the rod 2 is attached to a bearing pin 5 which also carries a star wheel 6. The rod 1 is attached to a bearing sleeve 7 journalled on the bearing pin 5. A second star Wheel 8 is attached on the sleeve 7. The two star wheels are in engagement with the driving device of the step selector so that both the rods can be pivoted in arbitrary direction to a certain extent irrespective of each other.

The rod 1 carries three of the movable connecting contacts 11, 12 and 13 of the step selector, one for each phase. The contacts are attached to the rods by means of screws 9. In the same way the rod 2 carries three similar connecting contacts 21, 22 and 23, also one for each phase. These contacts are attached by means of screws 10. Each contact consists of an angled part which is screwed to the rod and a clamp contact attached to the free end of the angled part and cooperating with the stationary connecting contacts of the step selector.

Each of the movable contacts in the example shown is arranged to cooperate with six stationary connecting contacts distributed uniformly around it. FIG. 2 shows how the movable contact 11 is in the same plane as the six stationary contacts 31, 32, 33, 34, 35 and 36 which are attached to insulating rods 37 and connected to alternate terminals on the control winding 14. The stationary contacts which are to cooperate with the movable contact 21 are located in a lower plane and these contacts are connected in turn to the other terminals on the control winding. This principle of arranging the stationary contacts and connecting them to the control winding is known per se.

The rod 1 carries three slip rings 15, each of which is electrically connected with one of the movable contacts 11, 12, 13. Similarly, the rod 2 carries three slip rings 24, each of which is joined to one of the movable contacts 21, 22, 23. Both the rods are placed inside the slip rings where they are stepwise pivotable in relation to each other. Since the two rods 1 and 2 which carry the movable contacts are arranged inside the slip rings, the pivoting movement of the rods around the bearing pins 3 and 5 will never be impeded by the brushes abutting the slip rings. The drawings thus show how the slip ring 15 joined to the contact 11 cooperates with the brush 16 which is connected to the lefthand stationary contact pair 18 of the load connector 17. The slip ring 24 in FIG. 1 is connected to the contact 21 and the brush 25 rests against the slip ring in FIG. 2, the brush being connected to the righthand contact pair 26 of the load connector. Similarly the movable contacts of the two other phases are connected one to each slip ring and joined via brushes to respective parts of the load connector.

With the arrangement proposed here the two carrier members are completely free from each other. The open construction enables easy fitting, adjusting or replacement of the contacts in the simplest possible manner and the two contact-carrying rods can be moved quite freely with respect to each other.

We claim:

1. Tap changer for transformers comprising a step selector and a load connector, wherein the step selector comprises a centre part provided with carrier members for movable connection contacts and slip rings for brushes which are connected to the load connector, the carrier members comprising two parallel rods (1, 2) of insulating material, means mounting each of the rods for turning around the axis of the centre part, each rod carrying a number of movable connecting contacts (11, 12, 13; 21, 22, 23) and a corresponding number of slip rings (15, 24), the two rods (1, 2) being positioned inside the slip rings (15, 24) whereby they are stepwise pivotable in relation to each other.

2. Tap changer according to claim 1, having connected to each rod a star wheel (6-, 8) which is in engagement with the driving device of the' step selector, each rod thus transmitting the driving torque for connecting contacts and slip rings mounted on it.

References Cited UNITED STATES PATENTS 3,366,750 1/1968 Bleibtreu 200-11 TC 3,614,597 10/1971 Van Riemsdijk 323,-43.5 R 3,652,812 3/ 1972 Ristuccia 200-11 TC GERALD GOLDBERG, Primary Examiner US. Cl. X.R. 

